Pressure measuring instrument



Oct. 10, 1933. J. M. SPITZGLASS 1,930,113

PRES SURE MEASURING INSTRUMENT Original Filed July 11, 1927 Jade/2 Z01ejcob dK djvitzgZa ss by Y (Wife/mi;

Patented ca. 10, 1933 UNITED STATES PATENT OFFICE Republic Flow MetersCompany, 111., a corporation of Illinois Chicago,

Original application July 11, 19:1, Serial No.

204,689. Divided and this application November 19, 19a1.- Serial No.570,030

scum. (Cl. 13-31) This invention relates. to pressure actuated measuringinstruments such'as flow meters.

This application is a division of my co-pending application, Serial No.204,689, filed July 11th,-

' the following description.

The invention is exemplified in the combination and arrangement of partsshown in the accompanying drawing and described in the followingspecification, and it is more particularly pointed out in the appendedclaims.

In the drawing:----

Fig. 1 is a diagrammatic sectional view illustrating one embodiment ofthe present invention;

Fig. 2 is an elevation with parts in section showing a flow meter bodyhaving the present invention applied thereto;

Fig. 3 is an elevation of chamber M and variations thereof, with partsin section, illustrating the principle of the invention.

In Fig. 1 of the drawing, the numeral designates a conduit for the flowof fluid having an orifice plate 21 disposed therein for producingdifferential pressure incident to the flow of fluid in the conduit.Closed body members 22 and 23 are connected by tubes 24 and 25respectively with the conduit 20 at the opposite sides of the orificeplate 21. The body member 22 is connected at the high pressure side andthe body member 23 at the low pressure side of the orifice plate. Amember M, open at its top forms a chamber within the body member 22 anda similar member C forms a chamber within the body member 23. The twochambers M and C are connected by a U-tube 26. The members M and C andthe U-tube are partially filled with mercury. It will be apparent thatthe legs of the mercury column will be subjected to the differentpressure at the opposite'sides of the orifice plate 21, so that themercury will rise in the member C to a height H above the mercury levelin the member M the distance H being dependent upon the differentialpressure produced in the conduit. The exteriors of the chambers M and Cwill be subjected to the same pressures as the interiors except for theeifect of the mercury columns within the members M and C. That is, thejoints between the members M and C and the U-tube 26, are not subjectedto thefull pressure in the conduit 20 so that the danger of leakage ofthe mercury is a minimum.

A cylinder 1, of insulating material is disposed within the chamber Cand a resistance R: is wound upon the cylinder 1 and forms a part of anelectric circuit supplied with electro-motive force from. thetransformer E and having an external resistance R1 therein- It will beapparent that the resistance R: will be changed by the height of themercury in the resistance chamber 0.

As explained in my prior Patent No. 1,325,763, the height of a liquidcolumn balancing a differential pressure produced by flow of fluid in aconduit is proportional tothe square of the velocity of the flow offluid in the conduit. It follows therefore that to make an electricalcur- II rent proportional to the flow of fluid passing thru the conduitit is only necessary that the current shall be proportional to thesquare root of the height of the liquid column balancing the velocitypressure or pressure difference created by the flow. It is desirabletherefore to wind the resistance wire R2 upon the cylinder 1 in such waythat the conductance of the electric circuit will be varied continuouslyby the rise and fall of the mercury level in the resistance chamber Cand at all times will be proportional to the square root of the heightof the mercury 71. in the resistance chamber C. The relation of thevarious quantities involved and the mechanism for laying the wire uponthe cylinder 1, are fully explained in my aforesaid copendingapplication.

In Fig. 2 there is shown the meter body of a flow meter constructedaccording to the present invention. The meter body comprises a basemember 27, on which the body tubes 22 and 23 are mounted and in whichthe chamber tubes M and C are disposed, the tubes M and C beingconnected by the U-tube 26. The cylinder 1 is supported within the bodytube 23, by an insulated rod 28 thru which the resistance wire Raextends to a terminal 29. A second terminal 30 is provided on the bodymember 23 thru which the circuit is completed to the mercury within theresistance chamber C. Valves 31 and 32 are provided for connecting thebody members 22 and 23 with the conduit 20. A valve 33 is provided forrelieving the pressure between the body members 22 and 23 if required.

The principle of operation is demonstrated diano grammatically inFig. 1. The U-tube partly fllled with mercury is made to balance thediiierential pressure 0! the flow in the pipe by the corresponding riseof mercury in 'the low pressure side of the tube. The mercury columnforms a part of the electric circuit as shown in the diagram.

The electric circuit contains a fixed external resistance R1 in serieswith a variable internal resistance R2, an electro-motive force E, aconductance indicator A, a conductance integrator or Mho meter W. Thevariable resistance R: is placed in the contact chamber C which formsthe low pressure side of the U-tube. The rise and fall of the mercurycolumn, produced by the variation oi the flow in the pipe, varies theamount of resistance and the corresponding amount of electricconductance in the circuit.

It can be seen from Fig. 1 that the effective height h, that is, therise of mercury in the low pressure side or the U-tube, has a definiterelation to the total difierential H. This relation is determined by therelative size of the legs of the U-tube and may be expressed by theequation:

where:

H=the height oi the mercury column balancing the pressure diiference orthe flow.

h=the rise of mercury in low pressure tube for a given pressurediiference.

or: the net mercury section in the chamber M.

az=the net mercury section in the chamber C.

Applying this principle to Fig. 2, it will be seen that the pressuredifferential, represented by the height H, necessary to produce a riseof mercury in chamber C, equal to height h is much greater than thatrequired to produce a similar rise or height h in Fig. 1, because therelative size 01 the legs of the U-tube has been varied.

From the foregoing, it will be evident that the range of the meter maybe changed, without changing the maximum rise of mercury or height itnecessary for a full scale deflection of the indicating instrument, byvarying the size of the legs of the U-tube. The change may be and ispreferably effected by changing the size of the chamber M relative tothe chamber C, although it is understood that either one or both of thechambers may be varied if desired. As illustrated in Fig. 3, the chamberM may be uniform in cross-section or it may have an enlarged portion M,the capacity of which may be further varied by a displacer M adapted toflt into said enlargement. Other forms of the chamber will suggestthemselves to those skilled in the art, as those shown are onlyillustrative. To permit the ready removal or interchange of the-chambers they are preferably threaded so that they may be detachablyconnected to the U-tube 26.

The chambers are maintained in correct position by spacer pins 34 whichengage the sides of the member 22. These pins prevent the chamber fromleaning to one side under the weight oi the mercury therein and thusrelieve the screw threaded connections of lateral strain.

Having thus described my invention what I claim is:

l. A measuring instrument comprising a pair of closed casings, a U-tubehaving the ends thereor disposed in said casings and opening into saidcasings, the portions of said U-tube in said casings having jointstherein, and means for subjecting the interior 01' said casings todiilerent pressures.

2. A meter body including a pair of closed casings, a U-tube having itsends opening into said casings, respectively, the portions or saidU-tube in said casings including chambers detachably connected to saidtube and means for subjecting the interior or said casings to differentpressures.

3. A meter housing including a pair of closed casings, an open toppedchamber in each of said casings, means providing communication betweensaid chambers and constituting. therewith a U-tube adapted to contain aliquid, and connections from said casings, respectively, whereby theinteriors of said casings and chambers may be subjected to differentpressures.

4. A meter housing including a pair or closed casings, a U-tube, thelegs of which are enlarged for a substantial portion thereof, and saidenlarged portions being detachably connected to the smaller portion,said enlarged portions and a part of the smaller portion being disposedin the casings respectively and means for subjecting the interior ofsaid casings to diflerent pressures.

5. A flow measuring instrument comprising a pair of elongated chambers,a connection between said chambers, said chambers and connection forminga U-tube adapted to contain a liquid, and

at least one of said chambers being detachably nections from saidcasings, whereby the interiors im thereof may be subjected to difierentpressures.

6. A meter housing including a pair oi! closed casings, a U-tubecomprising a plurality of sections detachably connected together andcontaining a conducting liquid, said sectional parts oflllS the U-tubeenclosed in said casings at the points of connection, means forintroducing fluid under pressure into said casings so that the interiorand exterior portions or said U-tube are exposed to said pressures andan indicating circuit including an element in said U-tube, theresistance of which is varied by rise and fall of the conducting liquidfor indicating variations in the quantity to be measured.

7. A measuring instrument, comprising a sectional U-tube adapted .tocontain a liquid, the sectional portions of said U-tube being detachablyconnected together, a casing inclosing said sectional portions of theU-tube at all points of detachable connection, connections to therespective casings for introducing fluid under pressure so as to exertapproximately the same pressure against both sides of the joints betweensaid sectional portions and means for indicating variations in height ofsaid liquid.

8. A pressure actuated instrument comprising a mercury containing U-tubehaving detachably connected enlarged portions at each end thereof,casings enclosing said enlarged portions and containing fluids underpressure, whereby the connecting joint between said enlarged portion andsaid U-tube is subjected on one side to said fluid pressure and on theother side to a pressure equal to said fluid pressure plus thedifferential weight 01. the mercury column above that of the fluidcolumn, acting on said joint.

JACOB M. SPlIZGLAS-S.

